Governor for impact wrenches



Nov. 4, 1941. A. AMTSBERG GOVERNOR FOR IMPACT WRENCHES 2 Sheets-Sheet '1 'Filed Sept. 28, 1940 5! BY v ATTORNEY Nov. 4, 1941. L. A. AMTSBERG 2,261,204 v GOVERNOR FOR IMPACT WR'ENCHES I 7 Filed Sept. 28, 1940 2 ShetS-ShGGt -2 Patented Nov. 4,1941

UNITED T Application September This-invention relates togovernors for controll in'g the speed of motors and has particular,

, but note'xclusi ve, application to im act wrenches driven by rotary air motors.

Impact clutches are usually designed .to respond. to the torque requirement of the driven bolt or nut, ,whereby during the free running 9 period the clutch imparts continuous or substantially continuous rotation, and under conditions of excessive torsional resistance "the clutch operates to effect a series'of disengagements and impacts. During the impacting cycle it is desir-' able to supply the motor with increased power thereby increasing the motor torque, the acceleration of-the rotary hammer assembly, andthe force ofthe blow. i

An object of this invention is to limit the free "running speed of an impact wrench, without interfering with the speed of the motor, or the supply of power thereto, during the impacting cycle.

Another object is to throttlethe air supply to the rotary engine while the impact clutch is -imparting-continuous rotation, by means of a governor which'is rendered ineifective durin the impacting cycle.

Further objects are to reduce air consumption, to increase the force of the blow, to provide a wider range of speed control and to prolong the life of the movable parts of'the wrench.

In accordance with the above and other objects, this invention provides a governor which is driven by the anvil element of the impact clutch instead of by the driving motor,,a in prior constructions. Thus the governor responds to the motor speed as long as the clutch drives the anvil continuously, but falls below the motor speed and thereby becomes inefiective .when the i 2,261,204., 5 GovEnNoR FOR. IMPACT WRENCHES I Lester A. Amtsberg, Cleveland, hio,-a'ssignor to Chicago Pneumatic ToolyCompany, New York, N. Y., a corporation of New Jersey U w 28,1940, Serial Nor-358,802 7'Claiih's.' (Cl.12l 34)f r I Fig. 4 is a-view similar tb Fig. "3, showing the hammer dogs in the driving or impact delivering position, parts of the carrier for th dogs being omitted;

Fig. 5 is a view, chiefly in longitudinal section, showing the centrifugal governor,'the control valve operated thereby, and the-elementsf which drive the governor;

Fig.-6 is an elevational view, looking iorward,

arrows 1 in Fig. 1.

Figs. 5 and 6 are on a considerably iargi scale than any of the remaining figures and show j v the governor actuated to a position whichlimits the flow of live air.

' The invention is "illustrated as' applied to an Y impact wrench-of the type in which the motor is .directly connected to the clutch hammer assemclutch begins impacting and the driving element of the clutch makes a much greater number of rotationsthan the driven or anvil member.

In the accompanying drawings which illustrate one embodiment or the invention Fig. 1 is a longitudinal section of a. reversible rotary impact wrench provided with the governor arrangement of the present invention, parts of the supporting handles being broken ofi;

Fig. 2 is a cross section througnthe impact v clutch, as indicated by the arrows 2 in Fig. 1,. illustrating the relation between the hammer bly, whereby the'motor repeatedly starts stops during the impact cycle.

Referring-particularly to Fig. 1, the illustra tive impact wrench comprises a governor house ing 10, a motor housing II, and a clutch housing i2, all detachably secured in fixed relation by any suitable means such as the usual arrange-T,

ment of bolts and flanges (not shown). The

.motor housing supports, on opposite sides, a dead handle it and a throttle valve handle it through which live motive fluid su'chas compressed air is admitted to the impact wrench. The top; of the governor housing is bolted to a spadehandle tion 52. I

A reversible housing ll includes a cylinder or'cylinder liner l8, the ends of which abut-against end plates 19. The rear. end plate has a peripheral-portion fltting the motor housing II and clamped between the cylinder l8 and governor housing 10. A gasket 20 may be interposed between the governor housing and the motor elements which include the motor housing II, cylinder l8 andrear end plate IS. The end plates are provided with an-, nular flanges 2| projecting away from'the cylinder and supporting ball bearings 22 forthe shafts of 'a rotor 23. The'body of the rotor i's in the form of a cylinder coaxial with the ball bearings 22. and defined by the end plates 19. As shown 55 in Fig.7, the cylinder It is arranged eccentrically and air motori-l'l 'wlthin the motor maximum size, and then diminish in size.

with respect to the axis of rotor 23, thus defining a crescent-shaped chamber 24 'therebetween. v

Arcuate slots 25 near the ends of the crescentshaped chamber provide'means for the admission and exhaust of pressure fluid thereto. The rotor has radial slots extending from end to end thereof in' which blades 21 are mounted for in-- ward and outward movement relative tothe rotor while the outer edges of the blades are maintained in contact with the inner wall of the cylinder. The blades divide' the crescent-shaped chamber 24 into a series of pockets, each of which is arranged to receive live air, disconnect the air from its source, expand in size as it revolves under the influence of the live air, exhaust after pointed out.

the motive fluid after the pocket has obtained In order that the inlet and exhaust may be properly timed without interfering with the reversibility of the engine, a set of relief ports or auxiliary exhaust ports 29 is provided on each side of the cylinder. The function of these sets of ports is to increase the effective length of the arcuate slots 25 which happen to be on the exhaust side, but not the slots on the inlet side. This is accomplished by a spring pressed plat 30 associated with each set of auxiliary exhaust ports and mounted for pivotal movement. The plate is movable out of the path o f-the ports 29 under the influence of the air being exhausted through said ports. On the inlet side, the valve 30 is held in a position closing the ports 29, under the combined influence of spring and live air pressure. I

The direction of rotation of the engine is controlled by a reversing valve32 (Figs. 1 and '1) mounted to turn in a bushing 33 seated in a recess at the side of the motor housing Ii. The

bushing has an inlet port 34 and an exhaust port 35 and the reverse valve has a pair of re-- cesses adapted selectively to connect inlet port 34 with one of the motor ports 3.5 or 31 and the exhaust port 35 with the other motor port. The

, reverse valve is manipulated by a lever 38 and,

is yieldingly locked in either extreme position by springs 33.

The impact clutch comprises an anvil 40 having impact receiving jaws 4|,and a pair of hama, squirrel cage, which revolves about the axis of the anvil 40. The plates 43 and 50 are centrally bored to receive bushings 52. The front plate 49 is held between the front end of the jaws 4| and a washer 53 seated on an annular flange at the rear end of the steel bushing 41. Washer 53 also serves as a retainer for the heads of the pivot Pins 43.

The rear plate 50 surrounds the cylindrical portion of a driving cam 54 and rotates approximately in unison with the cam as will be herein- The cam has a splined connection with the front end of the rotor shaft. Suitable washers 55 and 53 hold the cam and hammer assembly against axial movement relative to the anvil 40 and clutch housing l2. The hammer assembly is driven by a force acting on each of the dogs 42 in a direction offset from the pivotal axis thereof, whereby the driving force tends to rock the dog in a declutching direction. In front of the plate 50, the cam 54 has a pair of arms 51 seated in sockets 53 in the hammer dogs 42. In front ofthe sockets 53, the dogs 42 are provided with internal cam surfaces 53 adapted to ride over the anvil jaws 4|, as the hammer assembly rotates ahead of the anvil, and rock thedog about the pivot pin 43' in a reclutching direction. The center of gravity of the dog preferably lies within the path circumscribed by the axes of the pivot pins 43 so that when the dog is rocked to one extreme position or the other, it tends to remain there by centrii'ugal force.

Assuming that the motor I! is rotating continuously and the resistance to rotation of the driven nut N is slight, the rotor 23, driving cam 54, hammer dogs 42 and anvil member 4|! all mer dogs 42 which are mounted for limited oscillatory movement about respective pivot pins 43. The front portion of theanvil projects beyond the clutchhousing and is adapted for atfor driving a threaded nut N.. The front end or the clutch housing is counterbored to receive a resilient bushing made of oil resisting synrear end of the anvil is recessed to receive a pilot shaft 43 which has a loose -fit in said recess as well as in a similar recess at the front extremity of the shaft for the rotor 23 whereby the anvil is held in axial alinement with the rotor but is not always constrained to rotate in unison therewith.

The hammer assembly comprises front and rear carrier plates 49 and respectively which support the ends'of the pivot pins. A pair of spacer sleeves 5| v (Figs. 1 and 3)v also extend between the carrier plates and are bolted thereto. The spacer sleeves, carrier plates and pivot pins form a substantially rigid structure, resembling tachment atits extremity to wrench socket 45 rotate substantially in unison in the position shown in Fig. 4,. relative movement between the clutch elements being resisted by friction and centrifugal force. The clutch will disengage occasionally even under very light loads, but each disengagement will be followed by a re-en8age-' ment since the dogs are constrained to move in a reclutching direction following each disen-- Easement. When the driven nut N becomes seated against one of the elements being secured, the resistance to further rotation rises to a point far in excess of the torque of the motor. The impact clutch is then effective to cause the delivery of rotational impulses or hammer blows fiatly exceeding the maximum motor torque.

en a blow is delivered, the momentum of the driving assembly including the hammer dogs 42, carrier plates 43 and 50, and the rotor 23 is transferred in a very brief instant to the anvil and the motor is temporarily stalled. The driving'cam 54 then rocks the dog 42 in a declutching direction about the axis of the stationary pin' 43. The complementary cam elements 4| and 59 then rockthe dog back to the Fig.4 position for delivering a succeeding hammer blow.

. For a further description of the structure and speed to a comparatively low value, such as 800 mit impacting with the governor valve wide open,

the present invention involves the novel arrangement of a governor assembly driven by the anvil instead of by the motor.

Referring to Figs. 1 and 5, the governor rod 60 is disposed coaxially with the rotor 23 and anvil 4| and extends throughout practically the entire length of the motor and clutch'housing.

The lower extremity of the rod is secured to a hexagonal shank 6| by means which include a pin 62 and .a brazing connection -The shank 'fits a hexagonal opening in the anvil 40 and enables the rod 50 to be driven thereby; A sleeve 63 surrounds the rod 60 and spaces the pilot shaft 48 from the hexagonal shank. The upper end of rod Bil'has a splined connection with a governor body 64 which is seated for relative tuming movement in 'a recess at the'rear extremi y of the shaft for the rotor 23. The governor body is provided with two oppositely extending pairs of parallel arms 65 which support transverse pins 6% on which governor weights 6! are pivoted. The weights are provided with projections 68 engaging under a transverse'bar- 69 at the upper 'end of a push pin Ill. The push pin I is mounted in a recess at the rear end of governor body 64 and is arranged to be moved-relative to the governor body in a rearward direction by the centrifugal weights or in a forward direction by air pressure. The push pin abuts against the front end of a stem portion H on a governor valve I2 which is coaxial with the push pin an reciprocatesin unison therewith. Governor valve I2 is mounted in a .cage I3 which is screw threaded to the governor housing l8. A stop pin I5 extending diametrically'across the rear portion of the cage limits rearward movement of the valve i2. I3 is open continuously atv its rear end for the admission of live motive fluid, and is provided with one or moreperipheral portsIG by means of which said motive fluid may escape under the regulation of the'governor valve. The valve restores the hammer dogs to the Fig. 4-po sition,-

The governor cage centrifugal force acting rearwardly on valve 12 and thereby reduces the size of'the uncovered to area of the ports I6, and consequently the rate of flow of pressure'fluid to the motor and the speed ofthe latter. Conversely, a reduction in speed of the anvil! increases the opening at the-ports-li and, if the motor is unable to drive the anvil at the predetermined 'maximumspeed,

the openings Iiremain wide open. The selected speedcan be adjusted by changing the weights 61'.

I Briefly summarizing the operation, let it be assumed that the governor is arranged to limit the anvil speed to 800 R. P. M. and that the socket Sis starting to run up a nut offering at the time very. little resistanceto rotation. The

operator opens the throttle valve (notshown) -in'handle I4 admitting live air past the'governor valve I2 and reverse valve 32 to the motor II to rotate the latter in a" clockwise direction looking'forward. As long as the resistance 130" rotation is slight, the rotor23 hammer carrier 1 '49 and 50, hammer dogs 42,- anvil 40;]wrench,

socket and driven nut N all-rotate in unison with the parts in the Fig. 4 position. .As the anvil starts to rotate, the governor valve II starts from its fully open position and "moves rearward under the influence of .thecentrifugal weights 61 until it reduces the size of the opening IE to the extent that the anvil speed is held to 800 R. P. M. The motor speed will be the same except for an occasional rise above this amount: when the impact clutch releases and permits -the motor to make a half turnjahead of..th e anvil and then re-engages. IWhen the driven nut N becomes seated and its, resistance to further rotation .-increases abruptly, the hammer dogs 52 r are releasedfrom the anvil by a cam action and move from. the engaged position-shown in Fig. 4 I

to the lost motion positionshown in Fig. 3. The action :of' the complementary earns! 59 and-M the re-engagement between the dogs and. the anvil being accompaniedby an impact having a torsional force greatly exceeding the maximum I torque of the motor. -The disengagement and re-engagement'ofthe clutch is repeated and the impacts are delivered in rapid succession.

The action of the motor during the impact;

cycle'is to start and stop each time an impact is delivered, the motor making a half turn at a time.

' The acceleration of a rotary air motor under thus controls the fiow of air through a circuit beginning with a throttle valve (not shown) in the throttle handle I4, the bore in said handle,

registering passages I8 and I9 in the motor housing and the governor housing respectively,

the rearwardlyopen bore of governor cage I3, outlet ports 16, governor housing passageway 80,

- and ports. 8i and 3d entering the reverse valve 32 which admits air to one side of the motor II and exhausts the other side as hereinbefore described. The governor valve 12 is provided with longitudinal ports 83 which balance the air pressures at the rear and front, with the exception of the area occupied by the stem portion II. The unbalanced area at the rear of the governor valve I2 moves the valve and the push pin 10 these conditions is very great and the instantane ous speed of themotor may exceed 800 RP. M.

before the rotor has moved 180 from its stalled position. In order to obtain maximum force of blow, it is desirable to disable the governor, or

forward in opposition to the'thrust of the centrifugal weights 6'! until a balance is attained between fluid pressure and centrifugal-force.

By uncovering more or less of the area of the.

governor outlet ports 16, the governor controls the speed of the anvil 40 within reasonably close limits. Any tendency 6f the anvil 40 to exceed speed limiting mechanism, during the impacting cycle and permit the governor ports I6 to remain wide open during this period. The presentinvention accomplishes this end without interfering with the operation of the governor during the running-up period,'by drivingthe governor from theanvil, instead of from the motor as in prior constructions. The anvil does not move the governor valve to partly closed position during the impacting cycle because the meanspeed and the maximum instantaneous speed of the anvil are both much lower than the corresponding speeds of the motor. I

When the operator desires to loosen a bolt or nut, he turns the reverse valve 32 to its opposite position, places thesocket 45 over the bolt or nut and then opens the throttle valve. The opera-,- tion is similar tothe action above described, but

, the'maximum predetermined speed increases the rotary impact hammer arranged to drive said anvil and deliver a series of rotational hammer blows thereto, a fluid pressure rotary engine for driving said hammer, and a centrifugal governor for controlling said engine, characterized by operating means for said governor driven by the anvil.

2. An impact wrench comprising a rotatable anvil, a rotatable impact hammer arranged to drive said anvil, clutch means between the hammer and anvil for causing a succession of disen gagements and re-engagements therebetween, a rotary motor for driving said hammer, governor means for limiting the speed of the motor while the hammer is in driving engagement with the anvil, and means for rendering the governor means ineffective while the hammer is disengaged from the anvil.

3. A wrench comprising a rotary air motor provided with a rotor, a releasing clutch having a driving element rotatable substantially in unison with the rotor and having a driven element adapted to be attached to a wrench socket, a

governor for throttling. the air supply to said motor, said governor comprising a valve urged toward closed position by centrifugal means, characterized by operating means for said centrifugal means driven by the driven element of the clutch.

4. A wrench comprising a rotary air motor provided with a rotor, a releasing clutch having a driving element rotatable substantially in unison with the rotor and having a driven element adapted to be attached to a wrench socket, a governor for throttling the air supply to said motor,'said governor comprising a valve urged toward open position by compressed air and toward closed position by centrifugal means, characterized byoperating means for said centrifugal means driven by the driven element of'the clutch.

5. In a device of the character described, a rotary motor, a conduit for supplying power thereto, governor means interposing a variable resistance in said conduit to the power supply for controlling the speed of the motor, a clutch having a driving element connectedto the motor and having a driven element arranged to be dis- 1y rotate ahead of the anvil anddeiiver impacts,

connected periodically from the driving element to enable the motor at times to rotate faster than the driven element, and a driving connection between the driven element and the governor means.

6. An impact wrench comprising a rotary motor, a conduit for supplying power thereto, governor means .interposing a variable resistance in said conduit to the power supply to control the speed of the motor, an impact clutch driven by the motor and including a hammer arranged under certain conditions to rotate in unison with the anvil and under other conditions to repeatedand a driving connection between the motor and governor for limiting the motor speed while the hammer and anvil rotate in unison, characterized in that said driving connection is arranged to be broken to" remove the restriction on the power supply during the time that the hammer is rotating ahead of -the anvil.

'7. A power operated wrench comprising a centrlfugal governor, a rotary air motor positioned in front of said governor and controlled thereby, a clutch in front of said rotary air motor, said clutch including a driving element adapted to be driven by the motor and a driven element to be driven by the driving element, said clutch elements being arranged coaxially with the motor and governor, and a driving connection between the clutch driven element and the governor, said driving connection comprising a rod extending through aligned bores in the driven element and motor.

LESTER A. AMTSBERG. 

